The present invention relates to a disposable applicator containing a non-staining fingerprint composition and method of making the same.
Although there are other methods of identifying individuals, it has become readily apparent that fingerprints provide a relatively simple, unique and absolute means of identification that requires little cooperation from the subject. Since fingerprints are archived they must be permanent and because they are often captured by an electronic camera, the preferred color of fingerprint images is black. Printer""s ink, which contains carbon pigmentation, meets the requirements of image permanency and color and has been and is still being widely used. Generally the ink is stored in a convenient reservoir such as a tube (for application to a plate prior to the fingerprinting procedure) or in a pad (against which the person""s fingerprint area is pressed before being deposited onto a paper substrate).
The tube and plate system, while skill intensive and time consuming to use, lends itself to large scale fingerprint operations such as police stations etc. The ink pad system, while lending itself to smaller scale fingerprint operations, has disadvantages such as the need to periodically replenish the ink and store replacement ink.
Disposable ink coaters, while eliminating the need to replenish ink in a pad, are generally expensive on a per use basis. For example, see my U.S. Pat. No. 6,027,556 (xe2x80x9c""556 patentxe2x80x9d) which describes an applicator for a nonstaining ink in which an absorbent ink pad material made of a melt-blown calendared polyester fabric is encapsulated between two gas-impermeable sheets, heat sealed along their edges. A spine is provided along one end of the applicator to allow a user to grasp the spine after the sheets are opened and rub the pad across a subject""s skin such as his or her foot thereby coating that area with the nonstaining ink.
The least expensive ink coaters are in the form of ink foils. The foils are comprised of two superimposed strips of polyester film with a coating of viscous ink solution disposed between the strips. The ink is composed of carbon black and lanolin. See FIG. 1 of the drawings which illustrates a carbon pigmented ink and lanolin solution 10 deposited on a thin plastic film 12 and FIG. 2 which illustrates the ink sandwiched between the lower film strip 12 and an upper film strip 16. The strips, generally made of Mylar(copyright) (Mylar is a registered trademark of E. I. DuPont de Nemours and Company), are of the same length with a margin 14 at one end of each strip on which ink is not deposited during the manufacturing process. The inkless margins 14 are apparently designed to allow a user to separate the two strips. After the layers 12 and 16 of film are peeled apart, one or both of the strips may be placed on a flat surface such as a table or hood of a patrol vehicle with the ink side up so that the ink may be transferred to the subject""s fingerprint area in a conventional manner. The user thus has one or both surfaces from which to ink the fingers, palms, feet of a person to be fingerprinted. The tackiness of the ink keeps the strips intact until they are peeled apart by hand. The lanolin, because it has a melting point of about 107 degrees F and a softening point much less than that, is problematic because in warm environments the ink can migrate and impair the quality of the coating as well as leak out from between the strips of film. Typically, this type of carbon pigmented ink stains the skin severely and is difficult to remove because the tackiness needed to keep the coating and film intact also makes the ink adhere strongly to the skin. The typical foils can be hard to open because of the difficulty grasping the separate marginal areas 14 of the foil strips.
There is a need for an inexpensive fingerprint composition and disposable applicator therefore which overcomes the above problems.
A non-staining or inkless fingerprint composition and disposible applicator therefore, in accordance with the present invention, includes two substantially nonpermeable foil strips having substantially the same width. The strips are superimposed one on one another with one of the strips being slightly longer than the other to provide an extended free pull-tab. The shorter strip also has a free pull-tab which extends under (or over) the extended pull-tabs to physically separate the strips thereby enabling the fingerprint composition on one or both of the strips to be applied to a person""s fingertip area. A thin layer of an inkless (or nonstaining) fingerprint composition is sandwiched between the superimposed foil strips leaving a small peripheral border including the area between the extended and shorter pull-tabs free of the composition.
An inkless composition includes a solution of a color former which is semisolid at ambient temperature. The color former is characterized by forming a perceivable colorant product representing a person""s fingerprint when applied to the person""s fingerprint area and deposited onto a paper substrate in the presence of a developer. The color former may comprise one of the transition metal salts and the solvent may include glycol, glycol fatty acid esters, fatty acids, polyoxyethylene fatty esters or other reagents which are compatible with the color former and are sufficiently heat resistant to maintain the composition in a semisolid state at room temperature, e.g., about 100 xc2x0 F. or less. It is to be noted that the developer may be separate from the color former solution or an integral constituent thereof with a sufficient amount of chelating agent to inhibit reaction between the color former and developer until the composition is applied to the fingerprint area and deposited onto the paper substrate.
With respect to the method of making the disposable applicator with the inkless composition therein, I provide two substantially nonpermeable thin film strips of plastic foil approximately the same width with one strip being slightly longer than the other. For example, the strips may be cut from a suitable stock material such as a Mylar(copyright) plastic strip having a thickness of 0.001xe2x80x3-0.005xe2x80x3 and preferably within the range of 0.002xe2x80x3 to 0.003xe2x80x3. I also provide an inkless fingerprint composition with the constituents discussed above. The composition is heated to liquify the semisolid composition and then coated on one (or both) of the strips leaving a peripheral margin, including the area under the pull-tabs free of the composition. The strips are then superimposed on one another with the inkless composition sandwiched therebetween and left to cool to room temperature.
The invention may be best understood in reference to the following description taken in conjunction with the accompanying drawings.